Objective
In this article, I am going to explain, how to insert multi user or more than one user in Share point list.
About SharePoint list where value would be inserted
There is a list called TestingUser.
There is one column in list called UserTest.
This column is of type Person or Group.
Allow multiple selections are true.
Allow selection is set to People and Group.
TestingUser list looks like below,

How to Insert?Let us suppose, you need to add more than one user at single time in SharePoint List. Users' values may come from an Active Directory or metadata. All the users are in a string as comma or semicolon separated value. Let us suppose users are in below format. string usercontrolvalue = "dhananjay,arun,anoj,patra,mub";

We need to inert these multiple users in a column of type People or Group in SharePoint list. Step 1First we need to split name of all the users from the string. Since in our case users are comma separated so below code will make a string array with users as value at different index. string[] userarray = usercontrolvalue.Split(',');Step 2Now we need to convert users as string to SPFieldUserValue. Below function is taking user name as string and converting that into SPFieldUserValue.

_Web variable is denoting current web where List is part of. publicSPFieldUserValue ConvertLoginName(string userid){SPUser requireduser = _web.EnsureUser(userid);SPFieldUserValue uservalue = newSPFieldUserValue(_web, requireduser.ID, requireduser.LoginName);return uservalue; }Step 3We need to make instance of SPFieldUserValueCollectionSPFieldUserValueCollection usercollection = newSPFieldUserValueCollection();Step 4For all the user; we need to convert that as SPFieldUserValue then add that them to SPFieldUserValueCollection instance for (int i = 0; i < userarray.Length; i++){SPFieldUserValue usertoadd = ConvertLoginName(userarray[i]);usercollection.Add(usertoadd);}

Only we need to perform above said task. For your reference entire code as below, Entire code